Why Worms Don’t Get Lost

A pair of neurons function as the organism's internal compass.

A pair of neurons with a structure researchers likened to a TV antenna (inset) help C. elegans worms find food using Earth’s magnetic field.

Andres Vidal-Gadea

Many animals use Earth’s
magnetic field for
navigation, but exactly how
they detect it has been a puzzle —
until now.

For the first time, researchers at
the University of Texas at Austin
have pinpointed a specific pair of
neurons that act as a magnetic
sensor in the simple worm C.
elegans. The neurons function as
an internal compass, giving the
worm a sense of up and down,
likely to help them find food,
which varies in availability and
quality at different soil depths

.
By adding a fluorescent marker
to the neurons, researchers could
watch the pair light up when
exposed to magnetic fields. They
also observed that hungry worms
burrowed downward, where food
was likely to be more plentiful in
their natural environment, even
when they were in a lab setting
where no food was present. The
worms did this, however, only in
the presence of Earth’s magnetic
field. The worms would wander
aimlessly if researchers either
shut down the specific pair of
neurons or artificially canceled the
magnetic field.

These findings, published in eLife in June, could help uncover how more complex animals, such as birds, pick up Earth’s magnetic field.

[This article originally appeared in print as "Why Worms Don't Wander."]